Common acoustic devices equipped with a speaker and/or a microphone are provided with a grille that covers a front face, etc. of the speaker and/or the microphone in order to protect a speaker diaphragm, etc. and to prevent the entry of dust, etc. The grille has a plurality of through holes that allow the passage of sound. In such a case, when the region having the through holes is surrounded by a smooth surface having no through holes, the through hole-provided region looks as if it floats over the smooth surface. Therefore, in order not to degrade the exterior design of the device, non-through holes each provided with a bottom and having the same diameter as that of each through hole are formed around the through hole-provided region.
For example, a speaker grille disclosed in Patent Document 1 has a plurality of recessed parts (non-through holes) each provided with a bottom and having the same diameter as that of each hole part (through hole) on a design surface. Patent Document 1 also describes that the recessed parts each with a bottom are provided so as to coincide with a reinforcement rib on a back face of the speaker grille, without a decrease in the strength of the grille and without impairment of the appearance of the design surface in which a plurality of hole parts are provided as if they are continuous.